Chapter 05.00: Evaluation of Dry Curing with Saltpeter (with and without sugar)

Introduction to Bacon & the Art of Living

The story of bacon is set in the late 1800s and early 1900s when most of the important developments in bacon took place. The plotline takes place in the 2000s with each character referring to a real person and actual events. The theme is a kind of “steampunk” where modern mannerisms, speech, clothes and practices are superimposed on a historical setting.  Modern people interact with old historical figures with all the historical and cultural bias that goes with this.

Dry-cured bacon was a staple food for so many years and it warrants an evaluation of the process just described from my childhood! The oldest form of curing was done with salt only and nitrate salt curing or sal ammoniac curing was probably discovered accidentally. Very early on, I believe, urine and sweat from humans and animals alike were used for curing and preserving purposes. As humans worked out how to distinguish between different salts, sal ammoniac and saltpetre were used whenever it was available. Over time, as saltpetre overtook sal ammoniac in terms of its availability, this became the curing salt of choice to be added with bay or rock salt.

We should be under no illusion of the sophistication of these ancient communities. The earliest storage of meat was probably done in seawater or saltwater from salt springs and later even in freshwater. Water storage of meat evolved to dry salting where salts were rubbed into the meat. When salt only was used, the meat was left sufficiently long for the meat cell to break down and the reaction to take place with one of its amino acids, L-Arginine which would add an oxygen atom to nitrogen and form nitric oxide. The salt used to rub onto the meat changes from sodium chloride or salt only to salt and a little bit of saltpetre whenever saltpetre was available. The next major progression was to add sugar to the mix of salt and saltpetre.

Review of Dry Curing

Early on, humans worked out that meat is preserved by drying it in the wind and sun and rubbing salt on it. It is easy to see how they would have used these two in combination and that by leaving the meat for a few months, they would have noticed the curing colour of the meat developing.

In Chapter 2 we saw that meat, if left sufficiently long and if enough water is removed from it to prevent spoilage, will naturally develop the cured colour through the oxidation of the amino acid L-arginine which forms nitric oxide which is the curing molecule. This is the exact same molecule we still rely on to cure our bacon and hams today.

I want to take you through the different curing steps used by my grandparents one more time and gain an understanding of what happens in the various steps. I present the high point of dry curing or probably the ultimate way the process can be used. An Englishman, living in Canada, Robert Goodrich later insisted on the same system which was handed down to him when he was taught the trade of meat curing while working at the Smithfield market in London, over 50 years ago. He is arguably one of the best proponents of dry curing in the world today.

Each step in this process had to be discovered through trial and error over many centuries and even millennia. In this chapter, we will see how this mix developed from salt only to salt, saltpetre and sugar. We will see that following the practice of applying salt once, salt was applied twice before curers worked out that it is beneficial to have multiple salting steps.

Here then is the dry curing method in a step-by-step presentation.

Mixing the dry cure

The salt mix used to this day typically consists of salt, sugar, and nitrate (saltpetre).


The dry mixture is rubbed onto the meat and kept at a temperature between 2 – 4oC. The curing mix is completely dissolved in the moisture present in the meat. As a very general guide, the rate of penetration of the salt into the meat is estimated at around 2.5cm/ week. Micrococcal and Staphylococcus bacteria reduce nitrate to nitrite. Through a sequence of chemical reactions or through bacteria reduction, nitric oxide will form which reacts with the haem protein, imparting the characteristic pinkish/ reddish colour and flavour to the meat. More than one application of salt is required, and the meat must be turned over and restacked daily. In large curing operations, meat is salted and stacked in a curing bath. The following day it’s re-stacked in a second bath. Meat at the top is taken off first and placed at the bottom of the second bath and continues to stack so that what was below, this time at the top, re-salting as you go.

Equalizing or post-salting resting

After the initial cure is complete, the excess cure is washed off with cold water. This is to facilitate the closing of meat pores leading to a hardening of the surface and a considerable reduction in the drying rate. The equalizing step should be done for the same amount of time as the initial curing time at the same refrigeration temperatures of between 2 – 4o C. This is to ensure that the cure spreads evenly through the meat. Some hams call for this step to be a few months. It depends on the ham size, the ratio of lean surface to mass, pH, and the presence of intramuscular fat. The relative humidity is progressively decreased as this step progresses. Weight loss of between 4 to 6% can be expected. French hams are normally heated to between 22oC and 24oC for a week to dry them and “fix” the colour. The air velocity ought to be kept low, but the air circulation must be uniform to ensure uniform air temperature and relative humidity through the curing chamber. Otherwise, microorganisms could spoil the meat.


If smoke is applied, the meat is first dried for 2 – 3 days, with high humidity of around 66% to 75% with a very light breeze/airflow. High air velocities will influence the quality of dry-cured ham negatively. This will lead to the surface layer of ham or bacon drying out and collapsing. Internal and external diffusions should be the same to achieve an efficient and uniform drying process.

In the end, the meat needs to be tacky to the touch for the smoke to adhere during the next step. An ambient temperature for dry-cured bacon of between 7 – 13oC is recommended. After drying, the meat will be well prepared for smoking or the ripening stage.


Traditionally smoking was done in regions where drying was more difficult. It imparts a characteristic flavour to the hams and acts as a preservative. In bacon production, it is interesting that smoking was applied as an additional preservative for bacon destined for long sea journeys. This is one of the reasons why countries far from England, accessed by such long voyages by sea, became accustomed to smoked bacon and green, unsmoked bacon is not generally known in those countries while in England and Europe, it is a well-known version of bacon, enjoyed till today. Here in South Africa, I had the request from many British Expats, to produce unsmoked bacon for them while for South Africans, this is never an option.

When doing cold smoking there is “no” heat at all. This development took place in Westphalia in Germany, and we will delve into this fascinating history when we focus on the smoking of meat in Chapter 13.02.02: Robert Henderson and the invention of the smokehouse. It produced superior bacon and hams compared to hot smoking. According to this method, no heat is run through the chamber at all. All you need is a thin blue smoke. Smoke duration is between 8 and 48 hours. Rest overnight at room temperature. In between cold smoking, hang back at room temperature and not in the fridge since if you do, this will make the product wet again.

Smoking is typically done for a total of 48 hours:

Day one 8 hours, rest overnight; Day two 8 hours, rest overnight; Day three 8 hours, rest overnight; Day four, rest all day and overnight; Day five 8 hours, rest overnight; Day six 8 hours, rest overnight; Day seven 8 hours. This gives you 48 hours (6 x 8 = 48). The fact of a 48-hour curing time is very interesting. Why so long? The reason and the profound implications will be discussed later when we look at the role of smoking.

Keep an eye on the colour of the bacon/meat when you take it out of the smokehouse and again the following morning before placing it into the smokehouse — this alone will give you an indication of the depth/colour of the smoke you like — keep records.

Ripening and Maturing

The meat is now held in an air-conditioned chamber and ripened. Depending on the objective of the product, this can take anything from 14 days to 3 years. The longer time it takes to mature, the better the quality will be. “Increased time of ripening gives a higher degree of enzymatic degradation, contributing to taste and flavour of the final product and as a consequence yields a higher quality of dry-cured ham.” (Petrova, et al., 2015) Generally, temperatures vary between 5o C and some take this up to as high as 14 or even 20o C. Relative humidity is between 70 and 90%.

Temperatures for the drying-ripening of hams are different since the drying and ripening stage flows one another and there is not normally a smoking step for most hams (there are some with a smoking step and bacon will usually have a smoking step). Even so, drying-ageing temperatures for hams vary greatly. Iberian ham, for example, has the “drying–ripening split into three-time intervals: the first phase is maintained at 6 – 16oC, the second at 16 – 26oC and the third at 12–22oC. This temperature range with the adjusted air relative humidity provides necessary moisture diffusivity and allows the adequate activity of meat enzymes that leads to the formation of the distinctive quality of the final product.” (Petrova, et al., part 2, 2015) The higher the temp, the lower the humidity and the higher the airspeed, the dryer the end product and the greater the weight loss.

Evaluation of Final Product

Developing a process like this took millennia and was the province of artisan guilds where secrets were tightly guarded and passed on from generation to generation.

Vegetable Dies

Before saltpetre could be used in curing brines, it had to become generally available as fertiliser and as a key ingredient in gunpowder. Before we look at this, there is another development that is clouded by history, but once I identified it in Turkey, it became easy to spot it through the pages of culinary history. It is the practice of using vegetables in meat curing and one particularly noticeable record comes to us courtesy of German and Austrian cookbooks pre-1600s. It reveals that vegetable dyes were used to bolster colour in the context of salt-only-curing. It is well known that the Germans and Austrians were familiar with nitrate curing and, I will argue, they would have been acquainted with sal ammoniac as a curing salt also, but it was not always available.

When I learned of this practice, years ago, of using vegetable dies to colour the meat, I thought, probably like the author who wrote about it, that vegetable dyes were used for their function as a dye. Since then, I have tried a number of these vegetable dyes in meat curing and to my surprise, I still need to find one that adequately colours the meat to look appetising. Most of these lose their colour upon cooking and turn brown. I now suspect the real reason for the inclusion of vegetable components in meat curing is to access the nitrates which are inherently part of the makeup of many of these vegetables.

An excellent case in point is beetroot. One may think that it is added for the purple colour, but in fact, the colour fades upon heating. It is packed with nitrates which follows the same process as we by now are very familiar with namely the conversion of nitrates to nitrites through bacterial reduction after which chemical reduction or through bacteria the nitrites change into nitric oxide which cured the meat when it reacts with the proteins. We can therefore say that vegetable curing was done many centuries ago and that the “modern” trend of using vegetables to cure meat is not that “new” or “modern” after all. It is of the greatest importance that including these vegetables not only added the nitrates required but also performed a vital antioxidative role which reacts with free radicals in the meat, thus making it healthier. We will look at free radicals in a bit more detail later. For now, all you have to remember is that free radicals are, generally speaking, our enemies.

A beautiful anecdote comes from the Danish company, CHR Hansen about the development of plant-based fermentation curing in recent years. They initially developed this into a formal product where they sold the starter culture and the client had to add this to a plant material containing nitrates and this would be a main component in the brine and replace nitrates and nitrites as the starter culture bacteria would do the conversion to nitrite and the meat would be cured.

This never took off. Instead, spice suppliers did the work for the clients by taking the plant-based material, doing the fermentation and selling the plant-based material where the fermentation took place already as a brine solution to the bacon and ham factories. The European Union put a stop to the practice, forcing clients who want to go this route, to do the fermentation in-house. The reason why clients were interested in this was not for health reasons which I will touch on in a minute, but because in this way they only use a “natural product” and do not add sodium nitrate or nitrite directly to the brine in which case it must be declared on the ingredient list. This gave the suppliers a “clean” label, meaning fewer e-numbers on the ingredient declaration and no mention of nitrates and nitrites. In essence, it is a ruse because nitrates and nitrites were still added to the meat, albeit this being done “indirectly” through the plant material used.

The change in EU legislation gave the CHR Hansen project new impetus. This was, however, only presently. An incident occurred in 1977 which put the approach back on the map for them. They tell the story as follows. “By coincidence, the idea got a renaissance some years later. Producers of “white sausages” such as “Münchner Weißwurst“ or “Nürnberger Bratwürstchen” had occasional problems with a red centre of the sausages – in particular when there was more time between stuffing and heat treatment than usual. Analyses showed that also in “white sausages”, especially in recipes with added herbs, significant amounts of nitrate were found. In sausages with a red centre, there was nitrite found as well. Microbial analyzes of such sausages showed an exceptionally high number of Staphylococci before reaching 45°C in the centre. All those observations and the growing scepticism of the use of nitrite as well as the declaration of nitrite as a preservative led to the idea to utilize the reddening effect of “white sausages.” (CHR Hansen)

Some producers possibly (probably) moved to the use of plant-based fermentation curing in order to remove the words nitrate and nitrate from their ingredient lists and not for any inherent health benefit. The fact is that there actually are tremendous health benefits in the approach and is something to earnestly consider for exactly this reason. Remember that we said that we must consider the overall curing environment.  Adding vegetables with strong antioxidative ability to meat curing is a highly productive thing we can do to improve the overall “health score” of meat. Note that I did not say processed meat because iron in meat, especially red meat can become oxidised and form free radicals. Chemicals added to meat can also form free radicals, but it is important to know that meat does this on its own, especially when we fry it. What applies to ingredients added to meat, also applies to meat itself. To make the curing process the villain is unfair and ill-informed! The matter needs more careful consideration which is one of the reasons for this work. 

When we look at the addition of sugar to curing brines, we will return to the matter of vegetables added as curing agents as they go hand in hand. Let’s look next at a salt-only curing recipe that comes to us from Roman times.

Cato the Elder

Salt-only curing has been done since antiquity. A record exists from Cato the Elder who described in 160 BCE how a ham should be cured. In his Latin work, De Agricultura (On Farming), this Roman statesman and farmer, gives an ancient recipe for curing pork with salt.

“After buying legs of pork, cut off the `feet. One-half peck ground Roman salt per ham. Spread the salt in the base of a vat or jar, then place a ham with the skin facing downwards. Cover completely with salt. After standing in salt for five days, take all hams out with the salt. Put those that were above below, and so rearrange and replace. After a total of 12 days take out the hams, clean off the salt and hang in the fresh air for two days. On the third day take down, rub all over with oil, hang in smoke for two days…take down, rub all over with a mixture of oil and vinegar and hang in the meat store. Neither moths nor worms will attack it.” (

Cato may have imitated a process whereby hams are smoked over juniper and beech wood. The process was probably imported by the Roman gourmets from Germania. ( It is possible that the process of curing itself was brought to Rome by the military stationed in Germany. Many years later, it would be in Westphalia where the cold smoking of meat was invented.

The Mechanics of Salt-Only Curing

The curing of meat in a salt-only system happens through the oxidation of L-Arganine either through enzymes that are present in the meat or through enzymes present in bacteria which penetrate the meat. One of the products created is nitric oxide which is the curing molecule.

The reaction is driven by both enzymes in the meat and bacteria which accomplish the oxidation through enzymes. An enzyme accelerates the rate of reaction in which different substrates are converted to products through the formation of what is called an “enzyme-substrate complex.” An enzyme is very specific in terms of its activity. Generally speaking, each enzyme will speed up (catalyses) only one type of reaction and it will only do this for one type of substrate. This highly specific mechanism is often referred to as a “lock and key” mechanism. Enzymes are in other words highly specific and discriminate between slightly different substrate molecules. Another important feature of enzymes is that their function as a catalyst is at an optimal level over a narrow range of temperatures, ionic strength and pH. (Natureclean)

Bacteria are single-celled living organisms. They are typically enclosed in a rigid cell wall with a plasma membrane. Internally, they do not have well-defined organelles such as a nucleus. Bacteria can produce many diverse types of enzymes. They respond to their environment. In general, they can produce enzymes that degrade a wide variety of organic materials such as fats, oils, cellulose, xylan, proteins, and starches. The materials listed are all polymers that must be reacted with more than one type of enzyme to be efficiently degraded to their basic building blocks. To accomplish this, a specific “team” of enzymes are provided to attack each type of polymer. “For example, there are three different classes of enzymes (endocellulases, exocellulases, cellobiohydrolases) that are required to degrade a cellulose polymer into basic glucose units. All three types of enzymes are referred to as cellulases, but each class attacks a specific structure or substructure of the polymer. Acting individually, none of the cellulases is capable of efficiently degrading the polymer. Bacteria can produce the complete “team” of enzymes that are necessary to degrade and consume the organic materials present in their environment at any given time. Moreover, bacteria can produce multiple “teams” at the same time.” (Natureclean)

A further important feature of bacteria’s enzyme production is that it begins as soon as the bacteria begin to grow. “The cells must obtain nutrients from their surroundings, so they secrete enzymes to degrade the available food. The quantities of enzymes produced vary depending on the bacterial species and the culture conditions (e.g., nutrients, temperature, and pH) and growth rate. Hydrolytic enzymes such as proteases, amylases, and cellulases, etc. are produced in the range of milligrammes per litre to grammes per litre.” (Natureclean)

These particular conditions required for bacteria to multiply are equally important. Bacteria require a particular environment to thrive closely associated with temperature and pH.

Contrary to bacteria, enzymes are not living organisms. They have a limited half-life (minutes to days, depending on conditions). Like bacteria, they have optimal and less favourable conditions which determine the efficacy of their function. “They are proteins that are biodegradable and are subject to damage by other enzymes (proteases), chemicals, and extremes of pH and temperature. An important difference between enzyme-based products and bacterial products is that the enzymes can’t repair themselves or reproduce. Living bacteria, however, produce fresh enzymes on a continuous basis and can bounce back following mild environmental insults.” (Natureclean)

Bacteria can be either proteolytic or non-proteolytic. Proteolytic bacteria is a type of bacteria that can produce protease enzymes, which are enzymes that can break down peptide bonds in protein molecules. The result of proteolysis is therefore the breakdown of proteins into smaller molecules catalyzed by cellular enzymes called proteases. (Shirai, 2017)

Proteolysis in dry-cured meat products has been attributed mainly to enzymes found naturally inside the meat. On the other hand, Rodríguez (1998) found that the breakdown of proteins on hams may be due not only to enzymes inherently part of the meat, but also to microbial, enzymes.” A researcher from New Zealand who did a lot of work to understand the penetrationmof bacteria into meat is C. O. Gill. Gill (1977) came to the same conclusion years earlier when they found that bacteria are confined to the surface of meat during the initial multiplication phase or logarithmic phase of growth but when proteolytic bacteria approach their maximum cell density, they secrte enzymes that can break cells down which includes break down of the connective tissue between muscle fibres, allowing the bacteria to penetrate the meat. Further, non-proteolytic bacteria do not penetrate meat, even when grown in association with proteolytic species. (Gill,1977)

Gill (1977) found that the “penetration of meat by nonmotile bacteria (i.e. not mobile) and the rapid rate of advance of invading microorganisms indicate that physical forces are involved in the movement of bacteria through meat. Non-proteolytic species do not invade in company with proteolytic species probably because, with mixed cultures, penetration originates in the area of growth of a microcolony of the proteolytic species so that the non-proteolytic bacteria are excluded.” The production of enzymes that can breat cels down by the bacteria does not occur until the end of the initial growth hase or logarithmic growth when the meat is in an advanced stage of spoilage. Therefore, unless the meat has been treated with a chemicals designed to break the muscle structure down there should be no penetration of bacteria into fresh, healthy meat. Penetration of meat by bacteria, therefore, apparently results from the breakdown of the connective tissue between muscle fibres by proteolytic enzymes secreted by the bacteria.” (Gill, 1977) Shirai (2017) quotes Gill (1984) when he stated that bacteria migrate into meat via gaps between muscle fibres and endomysia. 

It has been shown that meat from a healthy animal is intrinsically sterile. The question then comes up of how bacteria are able to penetrate this very compact structure in a matter of days and weeks during tyhe curing of hams and bacon in dry-curing. Without the aid of some outside force, bacteria will spread through a meat muscle only by the time the meat is almost written. How is it possible for the meat to remain relatively “healthy” and bacteria penetrate it completely? What can this outside force be that facilitates its spread through the meat?

The answer is in the spread of the salt through the muscle. The salt molecule is large, but it splits into two ionic compounds, sodium and chloride which are much smaller and able to travel through the meat at a higher rate. The meat cells are dehydrated by the salt and the meat fibres shrink. Water migrates out of the cells and a large quantity lodge itself in the enlarged extra-cellular spaces inside the meat. This creates waterways for the bacteria to spread into the inner parts of the muscle much faster than it would have if it relied on its own ability to “bore” into the meat.

Another feature to take into account is that certain bacteria have the ability to switch respiration from oxygen to nitrogen for their metabolism. When oxygen is in short supply, these bacteria switch over to nitrogen respiration. The deeper the bacteria penetrate the muscle, the more it is devoid of oxygen and as its respiration change from oxygen driven to nitrogen driven, it requires access to nitrogen. It is at this point when the L-Arganine amino acid is accessed by the bacteria to gain access to the nitrogen and as it does this, nitric oxide is created as a byproduct of respiration which cures the meat.

Salt with a little bit of saltpetre

We know by now that nitric oxide can also be produced from nitrate salts such as sodium or potassium nitrate. One of the ancient nitrate salts is called Saltpeter. It was found that if a little bit of Saltpeter was added to the salt when rubbing it onto the hams or bacon, the curing reaction was sped up. The reason was, of course, that the bacteria now had an easier and more readily available source of nitrogen namely nitrate which is three oxygen atoms joined with one nitrogen atom. Saltpetre is the curing salt that most of us are familiar with that predates sodium nitrite as curing agent. 

By far the largest natural known deposits of saltpetre to the Western world of the 1600s were found in India and the East Indian Companies of England and Holland plaid pivotal roles in facilitating its acquisition and transport. The massive nitrate fields of the Atacama Desert and those of the Tarim Bason were still largely unknown. In 1300, 1400 and 1500 saltpetre had, however, become the interest of all governments in India and there was a huge development in local saltpetre production.

In Europe, references to natron emerged from the middle of the 1500s and were described by scholars who travelled to the East where they encountered the substance and the terminology. Natron was originally the word that referred to saltpetre. Later, the word natron was changed and nitron was used.

At first, the saltpetre fields of Bihar were the focus of the Dutch East Indian Company (VOC) and the British East Indian Company (EIC). The VOC dominated the saltpetre trade at this point. In the 1750s, the English East Indian Company (EIC) was militarised. Events soon took place that allowed for the monopolization of the saltpetre trade. In 1757 the British took over Subah of Bengal; a VOC expeditionary force was defeated in 1759 at Bedara; and finally, the British defeated the Mughals at Buxar in 1764 which secured the EIC’s control over Bihar. The British seized Bengal and took possession of 70% of the world’s saltpetre production during the latter part of the 1700s. (Frey, J. W.; 2009: 508 – 509)

The application of nitrate in meat curing in Europe rose as it became more generally available. Later, massive deposits of sodium nitrate were discovered in the Atacama Desert of Chile and Peru and became known as Chilean saltpetre. Curing with this was only a re-introduction of technology that existed since well before 2000 BCE.

The pivotal area where I believe saltpetre technology spread from across Asia, India and into Europe, is the Turpan-Hami Basin in the Taklimakan Desert in China. Its strategic location on the silk road, the evidence of advanced medical uses of nitrates from very early on and the ethnic link with Europe of people who lived here, all support this hypothesis.

Large saltpetre industries sprang to the South in India and to the Southeast in western China. In India, a large saltpetre industry developed in the north on the border with Nepal – in the state of Bihar, in particular, around the capital, Patna; in West Bengal and in Uttar Pradesh (Salkind, N. J. (edit), 2006: 519). Here, it was probably the monsoon rains which drench arid ground and as the soil dries during the dry season, capillary action pulls nitrate salts from deep underground to the surface where they are collected and refined. It is speculated that the source of the nitrates may be human and animal urine. Technology to refine saltpetre probably only arrived on Indian soil in the 1300s. Both the technology to process it and a robust trade in sal ammoniac in China, particularly in western China, predate the development of the Indian industry. It is therefore unlikely that India was the birthplace of curing. Saltpetre technology probably came from China, however, India, through the Dutch East Indian Company and later, the English East Indian Company became the major source of saltpetre to the West.

To the Southeast, in China, the largest production base of saltpetre was discovered dating back to a thousand years ago. Here, a network of caves was discovered in 2003 in the Laojun Mountains in Sichuan Province. Meat curing interestingly enough is also centred around the western and southern parts of China.

In China, in particular, a very strong tradition of meat curing developed after saltpetre was possibly first introduced to the Chinese well before 2000 BCE. Its use in meat curing only became popular in Europe between 1600 and 1750 and it became universally used in these regions towards the end of 1700. Its usage most certainly coincided with its availability and price. I have not compared price and availability in Europe with the findings on its use in meat curing which is based upon an examination of German and Austrian kook books by Lauder (1991), but I am confident that when I get to it one day, the facts will prove the same.

The Dutch and English arrived in India after 1600 with the first shipment of saltpetre from this region to Europe in 1618. Availability in Europe was, generally speaking, restricted to governments who, at this time, increasingly used it in warfare. (Frey, J. W.; 2009) This correlates well with the proposed time when it became generally available to the European population in the 1700s from Lauder. A strong case is emerging that the link between Western Europe and the desert regions of Western China was the place where nitrate curing developed into an art. Whether it happened here or in the lands surrounding the Black Sea is hard to tell. Wich region influenced this is uncertain but that both regions are very strong contenders for the development of curing into an art is certain. That these regions had a hugely symbiotic effect on one another is clear. It is highly significant that sea beat, the form of beetroot that existed before it was cultivated and became the plant we know today, comes from the northern shores of the Caspian Sea with the Caucus Mountains stretching from this water body to the Black Sea. In Turkey, still today, beetroot is a highly important crop and the industry stretches back to a time before historic records were kept.

Dry-curing of meat changed from salt only to a mixture of salt and saltpetre, liberally rubbed over the meat. As it migrates into the meat, water and blood are extracted and drained. The meat is usually laid skin down and all exposed meat is plastered with a mixture of salt and saltpetre. Pork bellies would cure in approximately 14 days. (Hui, Y. H., 2012: 540)

Salt, Saltpetre, and Sugar

The addition of sugar which favours the reduction of nitrate to the active agent nitrite became common practice during the 19th century.” (Lauer K. 1991.) At first, sugar was added to reduce the saltiness of the meat and make it more palatable. Curers soon discovered that when sugar is added, the meat cures faster and the colour development is better.

Science later revealed that the sugars contribute to “maintaining acid and reducing conditions favourable” for the formation of nitric oxide.” (Kraybill, H. R..  2009) “Under certain conditions reducing sugars are more effective than nonreducing sugars, but this difference is not due to the reducing sugar itself. The exact mechanism of the action of the sugars is not known. It may be dependent upon their utilisation by microorganisms or the enzymatic systems of the meat tissues.” (Kraybill, H. R.. 2009)

Ralph Hoagland, Senior Biochemist, Biochemie Division, Bureau of Animal Industry, United States Department of Agriculture, discovered that saltpetre’s functional value upon the colour of meat is its reduction to nitrates and the nitrites to nitric oxide, with the consequent production of NO-hemoglobin.

He wrote an important article in 1921, Substitutes for Sucrose in Cured Meats. Writing at this time, this formidable meat scientist is ideally placed to comment on the use of sugar in meat curing in the 1800s since the basis of its use would have been rooted in history.

He writes about the use of sugar in meat curing in the USA and says that it is used “extensively.” He reveals that according to government records, 15,924,009 pounds of sugar and 1,712,008 pounds of syrup, totalling 17,636,017 was used in curing meats in pickle in establishments that were inspected by the US Government, in 1917. If one would add the estimated use of sugar in dry cures in the same year, he placed the usage at an estimated total of 20,000,000 pounds. This estimate excludes the use of sugar in meat curing on farms. (Hoagland, R. 1921)

Hoagland says that the functional value of sugar in meat curing at this time (and probably reaching back into the 1800s) was entirely related to product quality and not preservation. “Sugar-cured” hams and bacon were viewed as being of superior quality. He states that a very large portion of bacon and hams produced in the USA are cured with sugar or syrup added to the cure. The quantity of sugar used in the curing mix is so small that it does not contribute to meat preservation at all.  He wrote that “meat can be cured in entire safety without the use of sugar, and large quantities are so cured.”  (Hoagland, R.  1921.)

The contribution to quality that he speaks about is probably related to both colour and flavour development. The colour development would have been related to the formation of the cured colour of the meat (The Naming of Prague Salt) as well as the browning during frying.

The role of sugar in bacon curing of the 1800s when saltpetre was used was elucidated in 1882 by Gayon and Dupetit, studying and coining the term “denitrification” by bacteria. The process whereby nitrate is changed to nitrite is through the process of bacterial denitrification. They demonstrated the effect of heat and oxygen on this process and more importantly for our present discussion, “they also showed that individual organic compounds such as sugars, oils, and alcohols could supplant complex organic materials and serve as reductants for nitrate.” (Payne, 1986)

Want to Know More?

The phrase used by Payne in his 1986 review article in celebration of a “Centenary of the Isolation of Denitrifying Bacteria,” quoted above caught my attention. “Individual organic compounds such as sugars, oils, and alcohols could supplant complex organic materials and serve as reductants for nitrate.” Did they mean to say that the environment becomes favourable for such reduction or did they mean to say that each of the organic compounds including sugars, oils, and alcohols could supplant the “complex organic material?” Did they mean this, that these materials somehow play a role in the actual reduction of nitrate or merely that it creates an environment for the existence of the bacteria required for the reduction to exist? It could only have been the latter because sugar plays no role in the actual reduction apart from being favourable for the microorganisms to exist which accomplish the reduction. Even Lauer (1991) whom we referred to above said that “the addition of sugar . . . favours the reduction of nitrate to the active agent nitrite. Payne in his review of the 100 years since denitrifying bacteria has been named mentions that Gayon and Dupetit were at this point being mentored by Pasteur and this fact alone necessitates that we pause for a moment and consider the word very carefully.

What is the exact nature of the “benefit” of sugar and is there something for us to learn here? The fact that sugar does not play any direct part in the reduction of nitrate is true but the fact that nitrate reduction takes place more rapidly when sugar has been added required more investigation.

Bacteria, like the cells of animals and plants rely on ATP as energy. Bacteria cannot process something without resources and the right environment. Temperature and pH accordingly are two very important environmental factors in the rate of microbial action. Another important factor is the availability of chemical nutrients. Jurtshuk (1996) puts it like this. “The uptake and utilization of the inorganic or organic compounds required for growth and maintenance of a cellular steady state (assimilation reactions)” is very important and lacking any of these can be a limiting factor on the microbes role such as nitrate reduction. They continue that “these respective exergonic (energy-yielding) and endergonic (energy-requiring) reactions are catalyzed within the living bacterial cell by integrated enzyme systems, the end result being self-replication of the cell. The capability of microbial cells to live, function, and replicate in an appropriate chemical milieu (such as a bacterial culture medium) and the chemical changes that result during this transformation constitute the scope of bacterial metabolism.” (Jurtshuk, 1996)

“The bacterial cell is a highly specialized energy transformer. Chemical energy generated by substrate oxidations is conserved by formation of high-energy compounds such as adenosine diphosphate (ADP) and adenosine triphosphate (ATP). . . ” (Jurtshuk, 1996) In order to do this, the bacteria requires a constant feed of particular chemicals. Carbon, nitrogen, Oxygen and Hydrogen are required. Our focus is on the conversion of nitrogen from Nitrate to Nitrite, but if carbon, for example, is not available, it becomes a limiting factor as the bacteria will stop converting nitrate to nitrite or the process will be slowed down considerably. Sugar turns out to be an excellent source of carbon for bacteria and adding sugar to a solution will increase the rate of nitrate conversion to nitrite in cases where the availability of carbon is limited. Seviour (1999) commented on the same phenomenan when he wrote that “the rate of denitrification is affected by several parameters including temperature, dissolved oxygen levels and the concentration and biodegradability of carbon sources available to these cells” (Seviour, 1999) Examples of such carbon sources are sugar, oxygen and plant oils. (FM)

Denitrifying bacteria are facultative anaerobes, that is, they will only use nitrate if oxygen is unavailable as the terminal electron acceptor in respiration.”  “The nitrate is sequentially reduced to more reduced forms although not all bacteria form gas. ” “Many bacteria can only carry out the reduction of nitrate to nitrite, and this process is referred to as dissimilatory nitrate reduction. There is also evidence emerging that certain bacteria can denitrify, even if oxygen is present.  (Seviour, 1999)

(Seviour, R. J., et al..  1999:  31)

What we have here are then two important reasons for adding sugar to the brine. In a Wiltshire live-brine system it will be to supplement the carbon for the bacteria’s diet which will enable them to convert nitrate to nitrite at an increased rate. In the past sugar was also added to reduce the “saltiness” of the bacon but in modern curing plants this is not a consideration any more. The fact that sugar adds to the taste and flavour of the bacon remains, however a reason why it is included in many brine cures.

A third possible reason why we want to include it is becasue nobody likes “pale” fried bacon. The best bacon has a dark golden colour when it is fried. The scandanavian countries, in particular are known for such bacon, but to some extent, it is a characteristic of good bacon the world over. This brings us to the topic of the reasons why these carours exist, as not all sugars are suitable for this and depending on the requirement, the optimal sugar must be selected.

There are two reasons why bacon turnes brown during frying. One is due to caramization and another is becasue of the Maillard reaction. In order to select the optimal sugar for these reactions, we devide sugars into two broad categories namely reducing and non-reducing sugars.

Redusing and non-Reducing Sugars and the Maillard Reaction

Sugars can be classified broadly into reducing and non reducing sugars.

>> Reducing Sugars

“Reducing sugars contain free aldehyde or ketone groups. They can transfer hydrogen electrons to other compounds and can cause the reduction of other compounds. the anomeric carbon of a sugar can be used to identify it. The first stereocenter of the molecule is an anomeric carbon. If the anomeric carbon has an OH group, it is a reducing sugar. When the sugar is in an open configuration, an alcohol molecule converts it to a ketone or aldehyde, which can reduce other compounds.” (Fernando)

Reducing sugar is a carbohydrate with a free aldehyde or free ketone functional group in its molecular structure. (Fernando)

Examples of reducing sugars:

– Glucose

– Fructose

– Galactose

– Maltose

– Lactose

– Dextrose

By this time you should have a proper headach trying to make sense of all of this. Dont worry. The only thing you actually need to remember is that for the Maillard reaction to take place, you need a redusing sugar. And a reducing sugar interacts with proteins during cooking or frying or baking which is what creates the brown/ caramel colour and apealing cooked flavours. For those who wonder, it is named after Louis Camille Maillard who first described it in 1912. We refer to it as the “browning reaction.” Other two important reasons why food turns brown is becasue of enzymes (called enzamic browning). You have seen when bacon is left uncovered in the freezer and it turnes brown. It is becasue of browning by enzymes. Another reason why bacon turns dark in colour upon frying is becasue of the caramalization of the sugars. Enzamic browning and caramalization has, however, nothing to do with the sugar being reducing or non-reducing. Caramalization occurs when reducing or non-reducing sugars are used.

>> Non-Reducing Sugars

“Non-reducing sugars do not contain any free aldehyde or ketone groups and are not capable of reducing other compounds because the anomeric carbon does not have an OH group attached to it.” (Fernando)

A non-reducing sugar is a carbohydrate that does not have a free aldehyde or free ketone functional group in its molecular structure. (Fernando)

“Sucrose is the most common non-reducing sugar. It is also known as table sugar. Sucrose is a glucose carbon connected at the anomeric carbon to a fructose carbon. Because the bond involves both anomeric carbons, neither carbon has an OH group. Therefore, sucrose cannot reduce other compounds and is not a reducing sugar.”

Examples of non-reducing sugars:

– Sucrose

– Trehalose

– Raffinose

– Stachyose

– Verbascose


The publication, Food Science, does a great job simplifying caramalization. They write, “Sugar molecules begin to disintegrate at temperature above 170 degree C (340 degree F). They break up in various ways, and the number of different compounds which can thus be yielded is over a hundred.” (Food Science)

“Some of them are brown in color and bitter in taste producing the characteristic color and flavour of caramelization. If heating continued, caramelized sugars break down further into pure black carbon. The various types of sugar differ noticeably in the extended to which they caramelize. Fructose and sucrose caramelize readily but dextrose (or glucose – practically the same substance) hardly does so at all. The pentose sugars whose molecules contain only five carbon atoms instead of six, caramelize very well. Since small amounts of these are present in wheat bran and in rye, wholemeal and rye breads tend to color quickly when toasted.” (Food Science)

“Caramelization can take place both in air and away from it, as at the bottom of a saucepan. The sticky black coating in the bottom of an overhead pan is mostly caramel and carbon. Caramelized sugar can be used as a brown coloring and is the basis of ‘gravy browning’, which is made from glucose.” (Food Science)

“An example of pure caramelization is the well-known dessert Crème Caramel. Sugar and water are boiled until the sugar is caramelized and this is then use to line a small mould. A vanilla flavored custard is poured in and the mould is placed in a bain-marie in the oven.” (Food Science)

In the 1800s when the use of saltpetre was at its pinnacle, the use of sugar with saltpetre had then a much more prominent role in that it energizes denitrification bacteria which results in an increased rate of nitrate reduction to nitrite and therefore would speed up curing with saltpetre and result in a better overall curing process. Today, with the widespread use of sodium nitrite in curing brines, certain denitrifying bacteria are one mechanism for NO formation which directly leads to better curing. The use of sugar or dextrose in bacon production in the modern era has more to do with the browning effect through the well-known Millard reaction to give fried bacon a nice dark caramel colour when fried.

Double Salting

The curer’s task was still to remove moisture from the meat as far as possible through salting. When this proved ineffective, another salting step was added. As you will see from the steps I gave you about dry-curing at the beginning of this chapter, double salting is incorporated there, but it has not been part of even dry curing for many decades. During the first salting, meat juices are pulled from the meat. This was cleared away and a second “salting” was administered. Later, several “salting’s” were administered as per the method of dry curing given. Right here from the southernmost point of the African continent comes a great illustration of this from the early 1700s which then, easily extends back several hundred years.

Remember that the settlement which became Cape Town was in the first place set up as a refreshment station for the Dutch East Indian ships that rounded the African continent en route to India from Amsterdam. It became a stop-over for any friendly ship and Cape Town soon got the name Tavern of the Sea. Here the summers are extremely hot from December to March or mid-April. Winter starts when the first Arctic cold fronts arrive in April and lasts till at least September. From September to December, it’s technically summer, but it’s often very cold and rainy with intermitted very hot spells. This means that April to August would be the only four months to properly cure meat which was very important for the Cape economy as it would be sold to passing ships. The pressure would have been relentless to find ways to cure meat in the other months also. This is then the background to the account of multiple salting’s.

Upham reports on the following course of events from 1709. A detailed treatment of the reference can be seen at Saltpeter, Horse Sweat and Biltong.

Michiel Ley who plays a key role in the story comes up with a plan to address the problem of the meat going bad before it is cured through. He suggests double salting. “Decided that the treat should first lie some days in the brine to draw out the blood, and after that placed in new salt. That was not the idea of Husing but of his fellow contract or Michiel Ley. The former believed that the meat should be left in its first salt and not pickled beforehand; And was prepared to guarantee supply remaining good.” This dispute clearly shows that double salting was by no means an accepted technique in the 1600s and early 1700s.

The decision was made. “Decided, however, to adopt the plan of double salting, recommended by Ley; Husing ordered to supply in that manner; “Meervliet” having brought sufficient casks for the purpose. Ley to supply his share according to his plan. Company to supply the pepper.” The meat which was previously salted by Husing was also given over to Ley. “Decided to take over for the Company, the meat already salted by Husing. The good portions to be distributed among the crews, & the tainted ones among the slaves …

So it happened that Lay was contracted to supply all the meat required by the Company together with Willem Basson, Jan Oberholster, and Anthony Abrahamsz. The issue of the supply of meat was major and shaped the immediate political landscape of the colony. Notice the black pepper which was added. The reason for this was probably to keep flies and other insects away.

Using Salt with Salpeter (or Sodium Nitrite) in a good plan (FM)

In the curing reaction we have been looking at, we begin with nitrate (NO3) which is converted through microorganisms into nitrite (NO2). Nitrite is then converted through a series of chemical reactions or through bacteria to nitric oxide (NO). Salt turns out to be one of the most important things we can add to nitrite that is dissolved in water to “motivate” the solution to form nitric oxide. We will see that there are a few “motivators” to form nitric oxide. I will point this out every time we talk about it because this will allow the factory manager or supervisor to pay special attention to those steps in the factory. This is because it is the simplest thing we can do to ensure that we cure the meat as completely as possible so that it is uniform in colour and taste great. Another such “motivator” we introduced in the chapter is smoking the meat which we will look at in much greater detail later on. How smoking meat was “formalised” in the dry curing system which Robert Goodrich tough me and in our modern systems is itself a fascinating story.

Want to Know more:

The most important additive that influences nitric oxide formation is salt, due to the formation of nitrosyl chloride (NOCl), which is a more powerful agent than dinitrogen trioxid. (Dikeman, M. and Devine, C..  2014: 417)  It was Ridd (1961) who first reported that nitrous acid and hydrochloric acid will generate nitrosyl chloride (NOCl).   (Ridd, J. H.; 1961: 418)


Curing is an art as old as humanity itself. It developed around the noblest of human pursuits namely to provide fuel for our inquisitive nature to explore the unknown. By itself, the story of meat curing stands in the annals of human achievement as a high point.

Future Research Project

We noted that Ridd (1961) reported that nitrous acid and hydrochloric acid will generate nitrosyl chloride (NOCl).  (Ridd, J. H.; 1961: 418) One of the products of ECA Water technology which we have been considering as a “tool” to cure meat more completely in order to eliminate residual nitrite is the formation of hydrochloric acid (HCl). How can this be exploited in designing an optimal curing procedure and mix?

I have looked with greater intent at sugar than I have ever done in my career. I realise that I can spend a year only looking at sugars. It is highly complex and the variety is immense. The impact on meat processing is huge.



CHR Hansen – pamphlet and private communication, 2021 and 2022.

Fernando, R. A Comparison of Reducing Sugar vs. Non-Reducing Sugar. Food Science

Gill CO, Penney N. Penetration of bacteria into meat. Appl Environ Microbiol. 1977 Jun;33(6):1284-6. doi: 10.1128/aem.33.6.1284-1286.1977. PMID: 406846; PMCID: PMC170872.

(c) eben van tonder

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